The iconic image of top U.S. officials—including President Barack Obama, Vice President Joe Biden, and then-Secretary of State Hillary Clinton—watching the raid that killed Osama bin Laden had been altered to include a white cat. The dazed-looking animal can be seen peering over the edge of the conference table.

Because the humorous addition didn't jibe with the serious tone of the column, readers initially thought it was an accident. On Tuesday, Krugman posted an update to the story clarifying that he used the image intentionally.

"Yes, I know there's a cat in the picture; I took it from Slate, 'The Cats of War,'" he wrote. "I've used that image before, to lighten things up slightly. Apparently I didn't succeed."